Optical as well as electro-optical modules, such as optical pumps, electro-optical modulators, optical amplifiers, transmitters, receivers, transceivers and the like, typically use a modified standard electronic housing to hermetically house optical and/or electro-optical components. Such a modified housing differs from the standard electronic package or housing in that an optical path(s) must pass through the wall of the housing, either thru a lens or an optical fiber.
In the prior art, optical modules typically use a so-called "14-pin butterfly" housing or package. Such an optical package includes an assembly platform, typically holding an optical fiber in alignment with an optical component, such as a laser or detector. More specifically, the optical component(s) is soldered to a carrier, and in turn, the carrier to the platform. Moreover, the optical fiber is encased within, for example, a ferrule soldered to an U-shaped clip, the clip soldered to another carrier, and in turn, that carrier soldered to the assembly platform so as to maintain the alignment between the optical fiber and the optical component(s).
During assembly, wherein the optical module is repeatedly subjected to elevated temperatures, such as during testing, soldering or when the module is hermetically sealed, undesired thermal stress in the module causes the fiber to move relative to the optical component(s), thereby drastically lowering the coupling efficiency. Reworking the optical module, such as through mechanical or thermal means, restores the coupling efficiency, but only by a limited amount. To reduce thermal stress, attempts have been made to match the thermal expansions of the carrier, sidewalls and platform of the housing, but have proven to be only partially successful.
Today, "14-pin butterfly" packages have an assembly platform made of a Cu--W composite, and carriers and sidewalls made of Kovar.RTM.. Although these materials have a similar thermal expansion, subjecting the optical module to elevated temperatures still dramatically lowers the coupling efficiency.
Accordingly, a need therefore still exits for the reduction of thermally induced stress in optical modules as well as electronic modules.